JPH0489455A - Novel ester compound, liquid crystal composition containing the same and optical switching element - Google Patents

Abstract

NEW MATERIAL:The ester compound of formula I [R and R' are (substituted) alkyl; X is single bond or O; A and B are group of formula II, formula V or formula VI and at least one of A and B is group of formula V or formula VI; Y is COO or OCO]. EXAMPLE:4-(2-Fluoro-2-methylheptanoyloxy)benzoic acid trans-4-(4octyloxyphenyl) cyclohexyl ester. USE:A component of liquid crystal composition. It can take a stable thermotropic liquid crystal state, give a ferroelectric liquid crystal composition having high spontaneous polarization and quick response when added to a non-chiral liquid crystal and is useful for optical switching element, etc. PREPARATION:A compound of formula I wherein Y is OCO can be produced by esterifying a phenol of formula III with a carboxylic acid of formula IV in a solvent (e.g. dichloromethane) in the presence of a dehydrative condensation agent (e.g. dicyclohexyl-carbodiimide) and 4-dimethylaminopyridine.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention can take a stable thermotropic liquid crystal state, and can be used, for example, in displays such as liquid crystal televisions, optical printer heads, optical Fourier transform elements, light pulp, etc. The present invention relates to a novel ester compound that can be used as a liquid crystal material that is useful as a material for optoelectronic devices that utilize liquid crystals and electrochemometry, as well as liquid crystal compositions and optical switching devices that contain this compound.

(Prior Art) Currently, liquid crystal compounds are used as display materials in various devices, and have been put to practical use in watches, calculators, small televisions, and the like. These devices use a cell mainly composed of a nematic liquid crystal material, and employ a display system called a TN type or STN type. In this case, the cell has a weak interaction between the dielectric anisotropy Δε of the liquid crystal compound and the electric field E (AεE2/2
), and the response speed to the electric field is several meters.
The disadvantage is that it is slow (seconds). Therefore, when used in televisions, an active matrix method in which a switching element is arranged and added for each pixel is mainly used as a drive method, which is one of the obstacles in achieving a larger screen. However, in 1975 R, B, Me
The emergence of ferroelectric liquid crystals, typified by 4-(4-n-decyloxybenzylideneamino)cinnamic acid-2-methylbutyl ester (DOBAMBC) synthesized by Yer et al., and N,A using it. , a new display method proposed by C1ark et al. (Applied Phys, Le
tt.

1980, Sara, 899), it became possible to create a liquid crystal cell with high-speed response on the μsec order and a property (memory property) in which the orientation of liquid crystal molecules does not change even when the electric field is turned off. Using display elements using these materials, it becomes possible to create liquid crystal displays using a simple matrix method using multiplex drive without using switching elements, and compared to active matrix devices, it is possible to improve productivity, cost, reliability, and larger screens. It will be much more advantageous in terms of conversion etc.

For this reason, many ferroelectric liquid crystal materials have been synthesized and proposed to date. In order for these ferroelectric liquid crystal materials to be used as display materials, several physical properties are required, but among them, the basic ones are that they exhibit a smectic C phase in a wide temperature range near room temperature, and that they exhibit large It has spontaneous polarization and is chemically stable. However, early ferroelectric liquid crystals had a spontaneous polarization of 10 nC.
They were chemically unstable because they were small (less than /cm2) and many had Schiff bases in their molecules.

Incidentally, the expression of large spontaneous polarization due to chemically stable ester compounds has recently been reported.

For example, the compound of the formula
It becomes a cholesteric phase liquid crystal in the temperature range of °C, but the spontaneous polarization of this liquid crystal at 83 °C is 89 nC/cm2
(Japanese Unexamined Patent Publication No. 61-43).

On the other hand, two-ring compounds have been synthesized in order to lower the temperature at which the xylsmectic C phase is exhibited.

For example, the biphenyl compound of the following formula exhibits a xylsmectic C phase from 44° C. upon elevation (Japanese Patent Laid-Open No. 118744/1983).

Furthermore, phenylpyrimidine compounds that stably exhibit a xylsmectic C phase near room temperature have been reported. For example, a compound of the following formula becomes a liquid crystal in a xylsmectic C phase in the temperature range of 40.7 to 82.8°C and a liquid crystal in a smectic A phase in a temperature range of 82.8 to 89.1°C. -200973
Publication No.).

(Problem to be solved by the invention! g) However, the above ester compound has a drawback that the temperature range of the xylsmectic C phase is narrow. In addition, the above biphenyl compounds include chiral smectate, riC
The temperature that shows the phase is close to room temperature, but the temperature range is about 10°
I can't say that C is wide enough.

Furthermore, the above phenylpyrimidine compound has a response speed of 4
It is estimated that the spontaneous polarization is as slow as 1500 μSec at 3°C and is quite small.

In other words, liquid crystal materials for display devices that require high-speed response must have large spontaneous polarization, low viscosity, or exhibit a xylsmectic C phase over a wide temperature range, including near room temperature. Physical properties are required, but the reality is that there is currently no material that satisfactorily satisfies these physical properties.

However, in recent years, compounds having fluorine on an asymmetric carbon have been synthesized, and attempts have been made to solve the conventional problems using these compounds. For example, a compound of the following formula having a fluorine and methyl group on an asymmetric carbon has been synthesized (
Special Publication No. 11-501394). However, when this compound is mixed with a pyrimidine-based Haese liquid crystal, it has poor compatibility and has the problem of causing the cholesteric phase of the Haese liquid crystal to disappear.

As a result of intensive studies to improve the liquid crystal properties of such compounds, the present inventors have found that by providing the compounds with a core structure having a cyclohexane ring or a pyrimidine ring instead of a biphenylene skeleton, thermotropic We have discovered that this compound can take a stable liquid crystal state, and that when this compound is mixed with Haese liquid crystal, it has properties that make it difficult to eliminate the cholesteric phase of Haese liquid crystal.

The present invention was made based on this knowledge,
The main object of the present invention is to provide a novel ester compound useful as a liquid crystal composition, and a liquid crystal composition containing the same.

Further, the present invention aims to provide a liquid crystal display element having high-speed response using a liquid crystal composition containing such a novel ester compound.

(Means for Solving the Problems) The present invention is based on the following general formula (I), (wherein R and R' are an alkyl group which may have a substituent, and X is a single bond or 10- 1A, B is Y is 1000-
The present invention relates to a novel ester compound represented by (or 10CO-), a liquid crystal composition containing this ester compound, and an optical switching element containing at least one kind of this ester compound as a constituent element.

In the above formula, when optical activity is imparted to the carbon to which -CH3 is bonded, a good optically active material can be produced by adding this to other non-optically active compounds.

Examples of representative compounds of the above formula and their physical and chemical properties are as follows.

■IR (KBr method, cm-'): 2910, 2B40.1775. 1710.1275
．． 1240.1110° Origin 4-(5-nonylpyrimidinyl-(2))phenyl NMR spectrum (90MH2, in CDCl3, TMS
Base δ value): 0.88 68 ml, 1-2.629Hn+ 1.68 3Hd 4.03 28t 5.01 1Hm 6.84 28d U= 9H
z)7.13 2t(d (J=
9Hz) 7.17 2Hd (J=
9Hz) 8.11 28 d (
J = 9Hz) U = 21Hz) (J = 7Hz) NMR spectrum (90MH2, TMS in CDCl3)
base δ value): 0.89 6Htn l, 1 to 2.1220+n 1.71 3Hd (J =
22Hz) 3.64 2Ht (J
= 7Hz) 7.28 2Hd
(J=9Hz)7.34 2Hd
(J=9Hz)8.30 2Hd
(J=9Hz)8.53 2Hd
(J=9Hz)8.64 2
8 s ■IRCKBr method, cm-'): 2910. 2B40. 1775. 1730. 1
430. 1268. 1190°1160.1055 Cyl)phenyl ■' H-NMR spectrum (90MHz.

standard, δ value): δ 0.89 68 m6 1.1~2
．． 6 16Hm δ 1.72 3Hd δ 7.13 2) 1 dδ 7.
25 2Hd 6 7.28 2Hd δ 8.27 2Hd ■IR (KBr method, cm-'): 2910, '2840.1775.1735.1270
In DC13, MS group 21Hz) 9Hz) 9Hz) 9Hz) 9Hz) 1200° 1160° In addition, the chain length of the alkyl chain of R and R' in the compound shown in the above-format (I), or the presence or absence of a substituent, It has an effect on the physical properties such as the temperature range in which the optically active liquid crystal material obtained by adding it to the non-optically active liquid crystal material can assume a liquid crystal state, and can be appropriately selected depending on the purpose.

In addition, as substituents for the alkyl group that may have substituents in R and R', lower alkyl groups, lower alkoxy groups,
A halogen atom, a trifluoromethyl group, etc. are preferred.

The compound of formula (I) above can be obtained as follows.

(I) When Y=-coo-: H3 (2) When Y.-0CO-: Further, the phenol (2) used here can be obtained as shown in the following formula.

That is, it can be obtained by esterifying carboxylic acid (I) and phenol (2) or phenol (3) and carboxylic acid (4) according to the above reaction formula.

As the esterification method, for example, a dehydration condensation method such as dicyclohexylcapodiimide can be used.

Alternatively, carboxylic acid (I) or (4) is converted into an acid halide using a halogenating agent such as thionyl chloride,
It is also possible to react with phenol (2) or (3) in the presence of a base.

Carboxylic acid (I) or phenol (3) used here
) are commercially available and can be used. Moreover, when synthesizing, it can be synthesized according to a conventional method and used.

(In the formula, Bn represents a Hensyl group.) That is, after esterifying 4-benzyloxyphenol and carboxylic acid (5) according to the above reaction formula, phenol (2) is obtained by deprotecting the benzyl group. .

Moreover, the carboxylic acid (4) used here can be obtained as shown in the following formula.

C13(3) That is, carboxylic acid (3) is obtained by esterifying 4-hydroxyhenzaldehyde and carboxylic acid (5) according to the above reaction formula and then oxidizing it.

In addition, the carboxylic acid (5) used here is R' as shown in the following formula.
-CF-COOH CHff (5) That is, first, according to the above reaction formula, 2-methyl-1゜2
- 2-fluoro-2methyl-2-fluoro-2-methyl-
1-Alkanol. By oxidizing this using an oxidizing agent such as potassium permanganate, rubonic acid (2) is obtained.
can be obtained.

(Example) Next, the present invention will be specifically explained using examples.

Cyclohexyl 4-hydroxyhenzaldehyde 0.63g, (-)
-2-Fluoro-2-methylhebutane MO, 59g
, dicyclo-xylcarbodiimide 1.09g, 4
0.05 g of -dimethylaminopyridine and 2M dry dichloromethane were placed in a flask and stirred at room temperature overnight.

The resulting solid was removed by filtration, the solvent was distilled off, and the oily substance was purified by silica gel column chromatography to obtain 4-(
0.84 g (yield: 87%) of 2-fluoro-2-methylheptanoyloxy)henzaldehyde was obtained.

The obtained 4-(2-fluoro-2-methylheptanoyloxy)henzaldehyde 0.84 g, potassium permanganate 0.50 g, potassium hydrogen sulfate 0.62 g and acetone 20% were placed in a flask and stirred at room temperature for 2 hours. did. After adding sodium bisulfite and 1N hydrochloric acid to reduce excess manganese, distilled water
d was added, extracted with dichloromethane, and washed with a saturated aqueous sodium chloride solution.

After drying over anhydrous magnesium sulfate and distilling off the solvent, 4-(2
-Fluoro-2-methylheptaturoxy)benzoic acid 0
．． 71 g (yield: 80%) was obtained.

■'H-NMR spectrum (90MHz, CDCh
Medium, TI'lS standard, δ value): 60.91 3Hm 6 1.1~2.2 88 m δ 1.72 3Hd (J = 20H
z) 67.24 21(d (J= 9H
z) δ 8.1B 2n d (J=
9Hz) δ 10.60 18 br, s ■
IR (KBr method, cm-'): 3300-2500.2910.2840.17?0.
1690.1600°1425, 1290.1200.
1160 1120 trans-4-(4-octyloxy)phenyl-1 cyclohexanol 216.2 mg
, 199.3111 g of the previously obtained 4-(2-fluoro-2-methylheptanoyloxy)benzoic acid, 170.2 μg of dicyclohexylcarbodiimide, 10.5 μg of 4-dimethylaminopyridine, and 15 ml of dry dichloromethane.
was placed in a flask and stirred at room temperature overnight.

The formed crystals were removed by filtration, the solvent was distilled off, and the resulting crude crystals were purified by silica gel column chromatography and recrystallization from ethanol to obtain 4-(2-fluoro2- Methylheptanoyloxy)benzoic acid trans-4-(4-octyloxyphenyl)cyclohexyl 165.9■ (yield 41%)
) was obtained.

The obtained target compound was injected into a 3 μm thick cell made of a glass plate with a transparent electrode coated with polyimide and subjected to a rubbing treatment, and heated at a rate of -2°C/min. However, when observed with a crossed Nicol polarizing microscope, the temperature was 82.7°C.
was directly crystallized from an isotropic liquid. Also, when the temperature drops, 83
．． At 8'C, the crystal changed to an isotropic liquid.

Breath M 4-(5-nonylpyrimidinyl-(2))pheny4-(5-nonylpyrimidinyl-(2))phenol 213.6■, 4-(2-fluoro-2methyl obtained in Example 1) heptanoyloxy)benzoic acid 199.6
■, dicyclohexylcarbodiimide 1718 mg,
8.9 ml of 4-dimethylaminopyridine and 15 ml of dry dichloromethane were placed in a flask and stirred overnight at room temperature.

The resulting crystals were removed by filtration, the solvent was distilled off, and the resulting crude crystals were purified by silica gel column chromatography and recrystallization from ethanol to obtain 4-(2-fluoro2) having the above-mentioned physical and chemical properties. -methylheptanoyloxy)benzoic acid 4-(5nonylpyrimidinyl-(2
)) Phenyl 265.1■ (yield 67%) was obtained.

Benefit 1 ■ The obtained target compound was injected into a 3 μm thick cell made of a glass plate with a transparent electrode coated with polyimide and subjected to a rubbing treatment, and the temperature was lowered at a rate of -2°C/min. When observed with a crossed Nicol polarizing microscope, the temperature was 87.4°C.
It changes from an isotropic liquid to a smectic A phase at 81.5
Crystallized at °C. Moreover, when the temperature was lowered, the crystal changed to an isotropic liquid at 100°C.

Disaster base 4-(2-fluoro-2-methylheptanoyloxy)
Benzoic ff 4-(I-trans-4-pentylcyclohexyl)phenyl 4-(trans-4-pentylcyclohexyl)phenol 175.1■, 4-(2-fluoro-2-methylheptanoyl obtained in Example 1) Oxy)benzoic acid 199
．． 4■, dicyclohexylcarbodiimide 161.2■
, 4-dimethylaminopyridine 9.3■ and dry dichloromethane 15/li! was placed in a flask and stirred at room temperature overnight.

The formed crystals were removed by filtration, the solvent was distilled off, and the resulting crude crystals were purified by silica gel column chromatography and recrystallization from ethanol to obtain 4-(2-fluoro2- 207.0 μm of 4-(trans-4-pentylcyclohexyl)phenyl methylheptanoyloxy)benzoate (yield 57%) was obtained.

The obtained target compound was injected into a 3 μm thick cell made of a glass plate with a transparent electrode coated with polyimide and subjected to a rubbing treatment, and the temperature was lowered at a rate of -2°C/min. When observed with a crossed Nicol polarizing microscope, it was 104.4°.
It was crystallized directly from an isotropic liquid at C. Also, when the temperature drops, 1
06°cT: Changed from crystal to isotropic liquid.

Implementation ±↓ Creation of liquid crystal composition and optical switching device Formula (6) below
, (7), (8), and (9) were mixed in the proportions shown below to prepare a base liquid crystal mixture A.

This liquid crystal composition A exhibited the phase transition behavior shown below.

(Cr indicates a crystalline phase, Sc indicates a smectic C phase, SA indicates a smectic A phase, N indicates a nematic phase, and ■ indicates an isotropic phase.) The second liquid crystal composition A does not contain a compound having an asymmetric carbon. Therefore, it does not exhibit ferroelectric behavior.

Next, this liquid crystal composition A and Example 2 represented by the following formula
A liquid crystal composition B was prepared by mixing the following compounds with the following compounds in the proportions shown below.

5.7 wt% Liquid crystal composition A 94.3 wt%
This liquid crystal composition B exhibited the following phase transition.

(Cr is crystalline phase, Sc″″ is xylsmectic C phase,
SA is smectic A phase, ch is cholesteric phase, ■
indicates an isotropic phase. ) This liquid crystal composition was also applied to a 2 μm thick glass plate with transparent electrodes coated with polyimide and subjected to rubbing treatment.
was injected into a cell, and the temperature was slowly lowered from the isotropic liquid state to align the cholesteric phase. When the temperature was further lowered to change the state from the smectic A phase to the chiral smectinoc C phase, well-oriented cells were easily obtained. When an electric field was applied to the cell while observing it with a cross-niffle polarizing microscope, clear switching behavior was observed.

Applying a 20Vpp square wave at 25°C to the above cell,
When the amount of transmitted light was measured with a photodiode and the optical switching operation was detected, the amount of transmitted light varied from 10% to 90%.
The time required for the change to % was 340 μs, which was very fast.

Liquid crystal composition A used in this comparison example 3 and special table 150139
A liquid crystal composition C was prepared by mixing the compounds of the following formula described in No. 4 in the following proportions.

Liquid crystal composition A 94.3wt% This liquid crystal composition C exhibited the following phase transition.

(Cr is crystalline phase, Sc" is chiral smectinic C phase, S
, indicates a smectic A phase, and I indicates an isotropic phase. ) Thus, since this liquid crystal composition C does not have a cholesteric phase, it is difficult to obtain good alignment.

(Effects of the Invention) The compound of the present invention can take a stable thermotropic liquid crystal state, and when added to a non-chiral liquid crystal, it becomes a ferroelectric liquid crystal composition with large spontaneous polarization and fast response speed. It has extremely excellent effects as a material for optoelectronics-related elements.

Therefore, the present invention can be said to be a liquid crystal material that is useful as a material for optoelectronic-related elements that utilize liquid crystals and electrochemical microscopy, such as displays such as liquid crystal televisions, optical printer heads, optical Fourier transform elements, and light valves.

Claims (1)

[Claims] 1. The following general formula (I), ▲ includes mathematical formulas, chemical formulas, tables, etc. ▼ (I) (wherein R and R' are alkyl groups that may have substituents, X is a single bond or -O-, A, B are ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ or ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼, and A, At least one of B ▲ has a mathematical formula, chemical formula, table, etc. ▼ or ▲ has a mathematical formula, chemical formula, table, etc. ▼, Y is -COO-
or -OCO-). 2. A liquid crystal composition containing at least one ester compound represented by the general formula (I) according to claim 1. 3. An optical switching element comprising at least one ester compound represented by the general formula (I) according to claim 1 as a constituent element.